It is well-known that UV-radiation can kill microorganisms in water such as bacteria, viruses, molds, algae, yeast, and oocysts like Cryptosporidium and Giardia. This knowledge is today applied in various water purification systems aiming at the production of safe drinking water. An example of such water purification system is a water purification system which incorporates a UV lamp around which water flows.
In all these systems it is essential that the water supply stops as soon the UV source diminishes, otherwise unsafe drinking water may be produced and consumed. Checking the UV intensity at the location where water purification should take place can be done by a UV sensor which, when connected to an electromagnetic valve, may stop the flux of water. An example of such a UV-sensor is disclosed in U.S. Pat. No. 3,413,465, which discloses an apparatus for sterilizing fluids, such as drinking water through the use of ultraviolet radiation. The apparatus disclosed in U.S. Pat. No. 3,413,465 comprises a valve assembly at the fluid inlet which is arranged to control the flow of water. The valve assembly comprises an electromagnetic valve using a metal ball and an electron magnet which is controlled by an external photochemical cell. When sufficient amount of UV-radiation is detected by the external photochemical cell, the electromagnet is energized and holds the metal ball so that it provides an open fluid inlet. When too low amount of UV-radiation is detected by the photochemical cell, the electromagnet is switched off, which results in that the metal ball in the valve instead covers the fluid inlet, so that no fluid can pass through the apparatus.
However for some applications a more autonomous response is desired. For example, in third world countries, sometimes use is made of the UV part of the UV-radiation spectrum of sun light to purify potential contaminated water. Especially at locations where use is made of sun light as UV source electricity is not always available. However, also in the case of lamp operated systems an autonomous system would be advantageous.
Therefore, there is still a need in the art to find new technical solutions for purification of water and other fluids.